Maine Orthoimagery Regional Midcoast 2009 (Imagery Layer)

This data set consists of 0.3-meter pixel resolution (approximately 1-foot), natural color orthoimages covering the urban area footprint. An orthoimage is remotely sensed image data in which displacement of features in the image caused by terrain relief and sensor orientation have been mathematically removed. Orthoimagery combines the image characteristics of a photograph with the geometric qualities of a map. The design accuracy is estimated not to exceed 3-meter diagonal RMSE (2.12m RMSE in X or Y). Each orthoimage provides imagery over a 1500-meter by 1500-meter block on the ground. There is no image overlap between adjacent files. The projected coordinate system is UTM with a NAD83 datum. The naming convention is based on the U. S. National Grid (USNG), taking the coordinates of the SW corner of the orthoimage. Task Order Number G09PD01896. USGS Contract Number 07CRCN0014. Nominal Acquisition Altitude (AGL) was 9600'. The geoid used to reduce satellite derived elevations to orthometric heights was Geoid 03. GPS coordinates are referenced to NAD83 Universal Transverse Mercator Zone 19. The maximum differential baseline length is 69373.00 meters. The mean baseline length is 25668.18 meters. Camera sensors calibration reports are included in the project report. Calibration flights are flown regularly. Natural color orthoimagery is organized in three color bands or channels which represent the red, green, and blue (RGB) portions of the spectrum. Each image pixel is assigned a triplet of numeric values, one for each color band. Numeric values range from 0 to 255. Areas where data is incomplete due to lack of full image coverage are represented with the numeric value of 0.本数据集包含分辨率为0.3米（约1英尺）的自然色正射影像（orthoimage），覆盖城市区域范围。正射影像是指经数学校正，消除了由地形起伏与传感器姿态导致的影像特征位移的遥感影像数据。正射影像兼具照片的图像特性与地图的几何精度特性。其设计精度估算值不超过3米的对角均方根误差（X或Y方向均方根误差为2.12米）。每张正射影像对应地面上1500米×1500米的区块，相邻文件间无影像重叠。其投影坐标系为以NAD83为基准面的通用横轴墨卡托（UTM）坐标系。命名规则基于美国国家网格（USNG），以正射影像西南角的坐标作为命名依据。任务订单编号为G09PD01896，美国地质调查局（USGS）合同编号为07CRCN0014。标称离地获取高度（Above Ground Level, AGL）为9600英尺。用于将卫星获取的高程转换为正高的大地水准面采用Geoid 03。GPS坐标参考于NAD83基准下的通用横轴墨卡托19带。最大差分基线长度为69373.00米，平均基线长度为25668.18米。项目报告中包含相机传感器的校准报告，校准飞行定期开展。自然色正射影像包含红、绿、蓝（RGB）三个光谱波段通道，每个影像像素对应一组数值三元组，分别对应各颜色波段的数值。数值范围为0至255，因图像覆盖不全导致的数据缺失区域，以数值0表示。